Abstract
The relationships between white spruce radial increment and wood properties were investigated in relation to tree and stand attributes using data from mature white spruce stands in the boreal forest of western Canada that experienced a range of shelterwood treatments. The model with the highest predictive ability was radial increment (adj-R2 = 67%) and included crown attributes, diameter at breast height (DBH), average height of competitors, and a climate index. Radial growth was positively related to live crown ratio, whereas wood density and modulus of elasticity were negatively correlated to the crown attribute. Tree slenderness had a significant negative effect on wood density and modulus of elasticity, as it reflects the mechanical stability requirement of the tree. The models consistently improved when using annual averages calculated over longer periods of time. However, when the annual averages were calculated using time periods of 5–10 and 10–20 years prior to sampling, the predictive ability of the models decreased, which indicated that the current tree and stand conditions were the best predictors of growth and wood properties up to five years prior to sampling. This study suggests that crown length equal to 2/3 of the tree height might represent an optimal balance between radial growth and wood quality.
Highlights
White spruce (Picea glauca (Moench) Voss) has high ecological and economic value and is a key component of the boreal forests of North America
This study developed predictive models of radial growth, wood density, microfibril angle, and modulus of elasticity using white spruce data from eight mature stands that underwent a wide range of shelterwood treatments in the boreal forests of western Canada
This study indicated that live crown ratio was overall the best predictor of radial area growth and wood properties of white spruce. [14] found a strong relationship between ring area and crown length when investigating Pressler’s law
Summary
White spruce (Picea glauca (Moench) Voss) has high ecological and economic value and is a key component of the boreal forests of North America. Shelterwood systems affect total stand density and the resources available for tree growth by partially removing the overstory canopy while protecting the advanced regeneration in the understory [5] These treatments have a strong influence on tree crown characteristics which in turn have direct effects on wood formation and fibre properties [6]. While climate information can be obtained [12], collecting crown and competition information is costly and time consuming, only one measurement per plot is often available In this regard, this study investigated the challenges related to modeling past growth rates and wood characteristics in relation to current crown attributes and competition levels. The base models were built using the three most recently produced annual rings to: 1—assess the influence of current crown and stand characteristics, and 2—test the predictive ability of the base models using time periods of different length and age
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